^^ Possibly, depending on what exactly the CPU is doing. If the game is running at 90% load, probably not, but if that load is shared with other processes, then its likely that the game isn't able to make full use of the CPU, and thus will execute at a slower speed.
with one 5870, my cpu is only taxed to about 45-50% while gaming. this is a good thing yes? cause the amount required to keep my game going is well below potential. if more is needed then its available. when i run 2 5870's, it puts me in the 90% range also, but still a little head room to work with.
what im getting at is, while your gpu is doing its job, it and the game are requesting enough info from your cpu to keep it at 80-98%. basically everything its got....almost. if you were sitting at 100% constant, then i would say you are being bottlenecked by your cpu, but not really "losing" any frames. with a overclock or cpu upgrade you could get more frames, but not are really lost per se.
Stupid question, But i need to know. If my CPU runs at say 90-98% at times in a game, does that result in lower frame rate?
I suggest you do some testing. Install fraps to measure frame rates.
a) Run your games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
b) Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 70%.
If your FPS drops significantly, it is an indicator that your cpu is the limiting factor, and a cpu upgrade is in order.
It is logical to me that as you improved your graphics capability, the cpu had to work harder to drive the new configuration to it's max.
Still, when any resourse gets above 70% or si, it indicates to me that that resource is becoming a limiting factor.
If your gaming experience is good, then don't worry about it.
If not, then look to see which improvement will be the more effective.